Reviewing the segment logic, notice that this visit would be in the Workspace fallout report, but not the Ad Hoc fallout report, as Page A does not have Campaign X.

Ad Hoc will evaluate the segment on a per fallout check point bases, where Workspace is just a sum of a sequential segment [page A THEN page THEN > page D] + the segment(s) the user adds. This can mean the data between Ad Hoc and Workspace may not match, especially when using a HIT level segment. This is because in essence the HIT level segment is being evaluated at a visit level. In this case was there a hit with campaign = X.